Firstly,
since the density in the accretion flow decreases outwards, the layers in the dusty part of the flow (where \(T\lesssim 1500\)  K) that are closest to the planet will likely contribute the most.
For \(T\gtrsim 700\)  K, only
silicate along with carbon, iron, or troilite remain
[1]}, [2]}.
Secondly,
in 2D simulations,
the pressure perturbation of the planet keeps the large grains outside of its orbit (“filters them out”; e.g. [3]}, [4]}, [5]}, [6]}).
For example, [7]} found a maximum grain size \(a_{\rm max}\sim 0.03\)  cm around the planet instead of \(a_{\rm max}\sim 3\)  cm at larger orbital radii in theirglobal-disc hydrodynamical simulations combined with a dust evolution model.
Also the size distribution near the planet is different, with
\(n(a)\propto a^{-q}\)  with \(q\approx 4\) , where \(n(a)\)  is the number density of grains of size \(a\)  (J. Drążkowska 2020, priv. comm.). This is steeper than the commonly used [8]} ISM distribution with \(q=3.5\) .
